Soft-Tissue Calcification in Uremia

The association between soft-tissue calcification (STC) and uremia has been recognized for more than 100 years,1but it is only since the widespread use of regular dialysis and transplantation that this has become an important problem.2 Virchow1surmised that calcium salts dissolved from bone were carried in the blood and deposited at some distant site to form "calcium metastases," a process analogous to the dissemination of cells from a primary neoplasm. In a review of 88 patients,"the underlying cause of metastatic calcification was nonmetabolic bone disease in 35, uremia in 23, primary hyperparathyroidism in 21, and vitamin D intoxication in 9. The lesions typically occur in the kidneys, stomach, lungs, and the left side of the heart, supposedly because of relative local alkalinity.4The essential feature of metastatic calcification is its occurrence in previously normal tissue exposed to an abnormal chemical environment, in contrast to dystrophic calcification which occurs in